There is no documented universal winner. AWS does not publish a head-to-head benchmark showing how many dollars of recoverable waste Trusted Advisor, Compute Optimizer or Cost Explorer finds across customer accounts. Their findings cover different things, can overlap, and depend on your resources, usage, pricing assumptions and enabled features. To estimate your own opportunity, compare the recommendations and their assumptions—not just the headline savings totals.
What each AWS tool actually finds
The three services are not interchangeable scanners. One focuses on a bounded EC2 rightsizing view, one analyzes resource configuration and utilization, and one presents best-practice checks that can surface recommendations from other AWS services.
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Cost Explorer: EC2 rightsizing opportunities
Cost Explorer’s named rightsizing recommendations feature identifies underutilized Amazon EC2 instances and can recommend downsizing or terminating them. It is useful for investigating EC2, but it is not a comprehensive scan for every kind of AWS waste. AWS points to Cost Optimization Hub for broader cost-optimization opportunities. AWS: Optimizing your cost with rightsizing recommendations
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Compute Optimizer: utilization-based resource recommendations
Compute Optimizer analyzes configuration and utilization metrics to recommend rightsizing and identify idle resources. Its resource-level context can help you assess the trade-off between cost and workload performance; projected usage views are available where supported. Recommendations still need validation against workload behavior and dependencies. AWS: What is AWS Compute Optimizer?
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Trusted Advisor: checks and surfaced actions
Trusted Advisor presents best-practice checks. For relevant newer cost checks, it can show the top Cost Optimization Hub action for a resource. Some checks require opting in to Cost Optimization Hub and Compute Optimizer. Because a check may relay an action produced elsewhere—and may show only the top action for that resource—it is better understood as a surfaced check-and-action view than as an independent, exhaustive savings engine. AWS Support: Cost optimization checks
Why their savings totals can overlap
Cost Optimization Hub is important to this comparison because it consolidates and prioritizes recommendations across accounts and Regions, considers commercial terms such as Reserved Instances (RIs) and Savings Plans, and includes rightsizing and idle-resource recommendations from Compute Optimizer. Its coverage extends beyond Cost Explorer’s native EC2 rightsizing feature. When Trusted Advisor surfaces a Cost Optimization Hub action, that result may overlap with a recommendation visible in the Hub or based on Compute Optimizer findings. Counting each displayed estimate as a separate opportunity can therefore overstate recoverable savings. AWS: Identifying opportunities with Cost Optimization Hub
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What the savings estimates assume
A recommendation’s dollar figure is modeled, not a promise of realized savings. The calculation method and pricing inputs matter when you compare totals.
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| Service or view | What the estimate is based on | What to keep in mind |
|---|---|---|
| Cost Explorer rightsizing | The calculation examines a recent 14-day instance usage period, considers On-Demand hours and applicable RI or Savings Plans coverage, and estimates the price difference for the proposed instance. AWS: Understanding rightsizing recommendations calculations | When the replacement stays in the same family, the calculation assumes a size-flexible RI covers it in the same way. It does not include second-order effects from reallocating RI hours to other instances. |
| Compute Optimizer | With savings estimation mode, it can account for Savings Plans and RIs; without that mode, its estimate uses On-Demand pricing. With Cost Optimization Hub enabled, recommendations can use data that includes account-specific discounts. AWS: Viewing EC2 instance recommendations | Check which estimation mode and integrations apply to the recommendation you are reviewing. A modeled saving may differ from the change in your actual bill. |
| Trusted Advisor cost checks | For relevant checks, the displayed action can be the top Cost Optimization Hub action for a resource. AWS Support: Cost optimization checks | Do not treat the displayed action as a separate, additive opportunity if the underlying recommendation is already counted elsewhere. |
How to compare findings in your own account
Use the services as complementary views, then deduplicate recommendations and validate the savings before acting. The sequence below is a practical comparison workflow, not an AWS-mandated order.
- Start with cost concentration in Cost Explorer. Use your billing view to identify where spend is concentrated, then inspect its EC2 rightsizing recommendations as a focused starting point. Do not interpret that feature as an inventory of all waste.
- Inspect Compute Optimizer recommendations and utilization context. Review the resource, its usage evidence and the proposed change. Check whether the estimate uses On-Demand pricing or savings estimation mode, and whether Cost Optimization Hub is enabled for account-specific discount data.
- Use Cost Optimization Hub to prioritize broader opportunities. Review its cross-account and cross-Region recommendations, including the effect of applicable RIs and Savings Plans. Treat a recommendation that appears in multiple views as one underlying opportunity unless you can establish that the actions are distinct.
- Check Trusted Advisor for surfaced best-practice actions. Confirm whether the relevant checks are enabled and whether an action is already represented in the Hub or Compute Optimizer.
- Validate before implementing. Check workload performance, dependencies and operational requirements before resizing, stopping or deleting a resource. Compare the projected bill impact with the actual commitment and usage changes you expect.
Timing can affect what appears after enrollment: AWS says Compute Optimizer findings may take up to 12 hours to generate, and specified Trusted Advisor results may take up to 48 hours to appear after opt-in. These are processing times, not savings estimates. AWS Support: Opt in AWS Compute Optimizer for Trusted Advisor checks
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which tool should you use first?
- For EC2 rightsizing: Start with Cost Explorer’s rightsizing recommendations, then inspect the utilization context in Compute Optimizer.
- For idle-resource and configuration-based findings: Use Compute Optimizer, checking supported resources and the pricing assumptions behind each estimate.
- For a consolidated, discount-aware view: Use Cost Optimization Hub, especially when you need to prioritize recommendations across accounts and Regions.
- For best-practice checks and surfaced actions: Review Trusted Advisor, while accounting for overlap with Cost Optimization Hub.
The documentation describes scope and estimation mechanics, not a comparative dollar ranking. Your account’s distinct, validated opportunities—not the sum of every number displayed across these services—are the meaningful measure of recoverable waste.
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